We have developed an innovative approach to the HIV/AIDS vaccine problem. Scientists have been working to target vaccines with adjuvant to dendritic cells (DCs) in vivo. Current strategies, however, have a significant potential limitation: vaccines are targeted only to classical DCs (cDCs) in the steady state. We hypothesize that inflammatory DCs, mobilized in large numbers and rapidly during infection, are important not only in innate defenses but in presenting antigens for adaptive immunity against invading pathogens including HIV. With the development of several monoclonal antibodies, we discovered a new subset of inflammatory monocyte-derived DCs (MoDCs) expressing mouse CD209a or DC-SIGN C-type lectin receptor. These inflammatory DCs accumulate in lymph nodes in 12 hrs upon lipopolysaccharide (LPS) treatment in a TLR4 dependent fashion, and also upon injection of LPS-containing bacteria. The novel inflammatory MoDCs are as effective or more effective than cDCs, even for cross presentation of antigens. Here we propose to harness inflammatory MoDCs to improve HIV vaccines with two specific aims in an R21 feasibility study in mice: (1) to identify optimal conditions for presentation of a model ovalbumin protein by inflammatory MoDCs in vivo;(2) to develop inflammatory MoDC-targeted HIV vaccines with improved immunity by targeting HIV Gag p24 and Env gp120 to CD209a+ inflammatory MoDCs with selected adjuvant(s) and route(s). Upon completing the R21 milestones, we propose, for the R33 phase, (3) to compare and then combine new MoDC-targeted and current cDC-targeted HIV vaccines for the development of a clinical strategy to maximize DCs in anti-HIV humoral and T cell immunity;(4) to prepare human/monkey MoDC-targeted HIV vaccines using the anti-human CD209 mAbs and evaluate their capacity to elicit combined B and T cell immunity in human CD209 mice;and (5) to determine the biology of CD209a+ MoDCs in mucosal tissues during inflammation and microbial infections for the development of a mucosal targeted vaccine strategy. This new vaccine approach to exploit inflammatory MoDCs might be effective in protection against broad spectrum of infectious agents. PUBLIC HEALTH RELEVANCE: This proposal will, for the first time, investigate inflammatory dendritic cells, as a focus for HIV vaccine development. Inflammatory dendritic cells are important immune regulating cells that are mobilized specifically during infection. Successful harnessing of inflammatory dendritic cells also impacts on developing vaccines against other infections and cancer.